This invention relates to a tool pivoting mechanism of a tool magazine for a machining center. In a conventional vertical machining center, there is generally a tool magazine to hold a variety of cutting tools. A disk type tool magazine and a chain type tool magazine are two of the most commonly used types. Whether it is a disk type or a chain type tool magazine, the tools held in the tool magazine are usually at a direction of 90 degrees angle against the main spindle. Therefore, before the changeover of a cutting tool, the tool must be rotated 90 degrees downward and parallel to the main spindle. Then, a tool transfer arm exchanges the tool in the main spindle with a tool in the tool magazine for the next step machining. The action of rotating a tool in the tool magazine downward for 90 degrees is generally called tool pivoting.
Referring to FIGS. 1 to 3, in a conventional vertical machining center tool (A) held in the tool magazine is disposed at 90 degrees against the main spindle (B). When there is a need to change a tool, tool (A) in the tool magazine must be pivoted 90 degrees and made parallel with the main spindle (B), then an automatic tool changer (C) and a tool transfer arm (D) are employed to exchange the pivoted tool with the tool in the main spindle (B).
Referring to FIGS. 4 and 5 for a conventional tool pivoting mechanism, a pressure cylinder (E) (pneumatic cylinder or hydraulic cylinder) directly actuates a tool pivoting block (F) which has a groove to allow a roller (H) to pass through. The roller is attached to one end of the tool pot (G) so that they can move together. During tool pivoting process, pressure cylinder (E) moves tool pivoting block (F) up or down, whereby roller (H) and tool (A) in tool pot (G) rotates 90 degrees by rotary shaft (I). Tool pivoting anchor block (J) and adjustable bolt (K) are used to control the correct angle and position of the pivoting tool.
The conventional tool pivoting mechanism set forth above using the pressure cylinder for actuation cannot precisely control the displacement, velocity, and acceleration of the tool pivoting process. Furthermore, the impact vibration occurred at the two ends of the cylinder displacement cannot be totally abolished by the buffer mechanism. Consequently, whenever the pressure cylinder reaches the end of displacement, a huge impact force usually occurs and makes the tool fall off the tool pot. This creates an unsafe situation which can injure the machining center operator.